I’ve spent the last few days studding OpenGL ES 2.0 Programming Guide by Aaftab Munshi, Dan Ginsburg & Dave Shreiner (Addison-Wesley Professional, ISBN: 0321502795). I must say It's a really good book. It leaves behind the legacy of the fixed graphics pipeline and makes it clear what APIs are relevant these days without any confusions. It's applicable to both embedded devices and desktop machines. It has no useless content, which is typical to the most technical books around, this fact I appreciate a lot. Greatly recommended!